|Title:||Application of duality principle to power-factor-correction converters|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Electric power factor
Department of Electronic and Information Engineering
|Pages:||xi, 96 leaves : ill. ; 30 cm|
|Abstract:||Power factor correction (PFC) is a topic of intense research in both academia and industry. Nowadays, many electric appliances are required to comply with international regulations regarding power factor and harmonic current contents. For a pure resistor, the voltage and current waveforms are in phase and no high frequency harmonic is induced. Thus, the power factor is unity. However, practical loads are not resistive. Thus, phase shift exists between the voltage and current waveforms. In theory, inductors and capacitors do not consume real power. The reactive power associated with them is not only a burden to the electric transmission network but also increases the stress to the appliances. Furthermore, high frequency current harmonics are induced by non-linear loads. Such harmonic currents cause electromagnetic interference (EMI) and pollute the power line network. Therefore, power factor correction and input current shaping are important design considerations in today's electronic products development. Duality principle plays an important role in circuit theory. It connects two circuits, which have apparently different topologies, but have similar properties when certain quantities and components are interchanged between the two circuits. It is a very powerful tool for circuit development because it provides a systematic way to generate new circuit topologies. A new converter, which employs inductive energy buffer, is implemented using this theory in this thesis. Many effective schemes for PFC were published in the past. In the first part of this thesis, a general overview of different types of PFC methods is given and a review of several traditional types of converters having PFC function and voltage regulation is described. Then, advantages and disadvantages of several major PFC schemes are presented. In the second part, the concepts of duality transformation are introduced. Based on the grafted tree and duality principle, a new single-stage cascaded pulse width modulation (PWM) PFC converter is developed. Analytical design expressions for the proposed converter are derived. Finally, experimental results, comparisons and future development are presented.|
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